This disclosure relates generally to the field of calipers used to measure internal dimensions of wellbores drilled through subsurface formations. More specifically, the disclosure relates to calipers with features to assist in seeking the largest internal dimension of a wellbore even under conditions of a well logging instrument “string” being held toward a bottom of the wellbore by gravity.
Various forms of calipers are known in the art for measuring internal diameter of a wellbore drilled through subsurface formations. Examples of calipers are described in U.S. Pat. No. 4,914,826, “Decentralized Well Logging Apparatus for Measuring the diameter of a Borehole Along Its Perpendicular Diametrical Axis”, issued to Nold, and U.S. Pat. No. 2,102,080, Well Surveying Device, issued to M. M. Kinley. Other calipers may be associated with various sensors, for example gamma-gamma density sensors or “dipmeter” or formation imaging sensors. See, e.g., U.S. Pat. No. 4,529,877 issued to Arnold.
There continues to be a need for calipers that can seek a largest diameter of the wellbore even when the instrument string is drawn to the bottom (lower side) of the wellbore by gravity.